Thermal or Viscous? Clutch fan.

The fact that it has one of those thermostatic spring coils on the front makes me think it's thermal...
Yeah that's what I was thinking after I posted it. I just picked it up an hour ago, took a picture without my glasses on. Only when I viewed the post did I notice that. Still I suppose it could activate by centrifugal force? IDK. Trying to figure out how to test it, don't want to buy a new clutch if this one is good, or if they're serviceable.